Surface acoustic wave properties of ZnO films on {001}-cut 〈110〉-propagating GaAs substrates

Abstract

GaAs has been employed as a material for acoustic charge transport (ACT) devices principally because it is a piezoelectric semiconductor. However, because GaAs is a weakly piezoelectric material, the surface acoustic wave (SAW) interdigital transducer (IDT) drive power required to achieve charge transport is typically about 27 dBm. An enhancement of the piezoelectric coupling could potentially improve device lifetime, reliability, dynamic range, and decrease device power consumption. To this end the use of a ZnO film on top of an ACT-like substrate to enhance the piezoelectric coupling has been investigated. Moreover, the ZnO film structure would also make it possible to monolithically integrate SAW devices and GaAs electronics. In order to provide a basis for the design of such devices, SAW properties are reported, including velocity, effective piezoelectric coupling constant, and attenuation, measured on ZnO films sputtered on {001}-cut 〈110〉-propagating GaAs substrates. The measurements have been performed for the different film thicknesses over the range of 1.6–4 μm and with films of different grain sizes. IDTs operating between 180 and 360 MHz were fabricated, and a knife-edge laser probe was used to measure the SAW propagation. The measured data for the velocity shows good agreement with theoretical values. The quality of the dc triode-sputtered films was superior to that of the rf magnetron-sputtered ones due to higher K2 and less attenuation. The value of K2 for the 1.6-μm-thick dc triode-sputtered one was measured to be 0.75% which is comparable with 1.07% for bulk crystalline ZnO.

The vibration and photoluminescence properties of one-dimensional ZnO nanowires

“…Compared to other wide band gap materials, ZnO possess a higher exciton binding energy of 60 meV [4] and low-power thresholds for optical pumping at room temperature, which is an advantage for the excitonic-related device applications [5,6]. In other applications, ZnO can also be used in transparent conducting layer and surface acoustic wave (SAW) devices [7][8][9] as piezoelectric layer and SAW sensors [10,11].…”

The characteristics of low-temperature-synthesized ZnS and ZnO nanoparticles

“…Due to higher exciton binding energy of 60 meV, ZnO has more efficient exciton emission at room temperature [7]. It can also be used in surface acoustic wave (SAW) devices [8][9][10] as piezoelectric layer and SAW sensors [11][12].…”

Generation and enhancement of surface acoustic waves on a highly doped p-type GaAs substrate

“…First, the piezoelectric coupling coefficient of GaAs is much smaller than those of commonly used piezoelectric materials such as ZnO, LiNbO 3 and AlN; thus only weak SAWs can be generated. [13][14][15] Second, when a piezoelectric substrate, in this case, GaAs, has been doped, the concentration of free carriers increases, leading to an electrical screening of the radio frequency eld applied on the IDTs, and results in a restraint of the generation of SAWs. 7,16,17 To resolve this electrical screening issue, researchers such as J. Rudolph et al 16 and A. Violante et al 7 both came up with a similar method to place the doped layer away from the surface layers where SAWs were generated and propagated.…”